PHP array functions (merge, split, append, find, delete, etc.)

1. Merge array

array_merge() Function to merge arrays together , Returns an associative array . The resulting array starts with the first input array parameter , Add the following array parameters in the order they appear . In the form of ：

array array_merge (array array1 array2…,arrayN)

This function combines the cells of one or more arrays , The values in an array are appended to the back of the previous array . Returns an array as a result .

If the input array has the same string key name , Then the value after the key name will overwrite the previous value . However , If the array contains a numeric key name , The latter value will not overwrite the original value , It's attached to the back .

If only one array is given and the array is digitally indexed , The key name is re indexed in a continuous manner .

<?php $fruits = array("apple","banana","pear"); $numbered = array("1","2","3"); $cards = array_merge($fruits, $numbered); print_r($cards); // output // Array ( [0] => apple [1] => banana [2] => pear [3] => 1 [4] => 2 [5] => 3 ) ?>

2. Append array

array_merge_recursive() Function and array_merge() identical , You can combine two or more arrays , Form a joint array ． The difference between the two is , When a key in an input array already exists in the result array, the function will take different processing methods ．array_merge() Will overwrite the previously existing keys / It's worth it , Replace with the key in the current input array / It's worth it , and array_merge_recursive() Will merge the two values together , Form a new array , And take the original key as the array name . There is also an array merge form , Is to recursively append an array . In the form of ：

array array_merge_recursive(array array1,array array2[…,array arrayN])

The program example is as follows ：

<?php $fruit1 = array("apple" => "red", "banana" => "yellow"); $fruit2 = array("pear" => "yellow", "apple" => "green"); $result = array_merge_recursive($fruit1, $fruit2); print_r($result); // output // Array ( [apple] => Array ( [0] => red [1] => green ) [banana] => yellow [pear] => yellow ) ?>

Now key apple Point to an array , This array is an indexed array of two color values .

3. Linked array

array_combine() Function will get a new array , It consists of a set of submitted keys and corresponding values . In the form of ：

array array_combine(array keys,array values)

Be careful , Both input arrays must be the same size , Can't be empty . Examples are as follows

<?php $name = array("apple", "banana", "orange"); $color = array("red", "yellow", "orange"); $fruit = array_combine($name, $color); print_r($fruit); // output // Array ( [apple] => red [banana] => yellow [orange] => orange ) ?>

4. split array array_slice()

array_slice() Function will return part of the array , From the key offset Start , To offset+length End of position . Its form ：

array array_slice (array array, int offset[,int length])

offset When it is a positive value , The split will start from the beginning of the array offset Position start ; If offset negative , From the end of the array offset Position start . If optional parameters are omitted length, Then the split will start from offset Start , Until the last element of the array . If given length And it's a positive number , Will be at the beginning of the array offset+length End of position . contrary , If given length And negative , Then... From the beginning of the array count(input_array)-|length| End of position . Consider an example ：

<?php $fruits = array("Apple", "Banana", "Orange", "Pear", "Grape", "Lemon", "Watermelon"); $subset = array_slice($fruits, 3); print_r($subset); // output // Array ( [0] => Pear [1] => Grape [2] => Lemon [3] => Watermelon ) ?>

Then we use the negative length ：

<?php $fruits = array("Apple", "Banana", "Orange", "Pear", "Grape", "Lemon", "Watermelon"); $subset = array_slice($fruits, 2, -2); print_r($subset); // output // Array ( [0] => Orange [1] => Pear [2] => Grape ) ?>

5. Join array array_splice()

array_splice() The function deletes from the array offset Start to offset+length All the elements of the end , And return the deleted element in the form of array . In the form of ：

array array_splice ( array array , int offset[,length[,array replacement]])

offset When it is a positive value , Then the join will start from... From the beginning of the array offset Position start ,offset When it's negative , The join will start at... From the end of the array offset Position start . If you ignore the optional length Parameters , From offset All elements from the beginning of the position to the end of the array will be deleted . If given length And it's positive , The join will be at... From the beginning of the array offset + leng th End of position . contrary , If given length And it's negative , The combination will be at the beginning of the array count(input_array)-length End of position for . Examples are as follows ：

<?php $fruits = array("Apple", "Banana", "Orange", "Pear", "Grape", "Lemon", "Watermelon"); $subset = array_splice($fruits, 4); print_r($fruits); print_r($subset); // output // Array ( [0] => Apple [1] => Banana [2] => Orange [3] => Pear ) // Array ( [0] => Grape [1] => Lemon [2] => Watermelon ) ?>

You can use optional parameters replacement To specify an array that replaces the target part . Examples are as follows ：

<?php $fruits = array("Apple", "Banana", "Orange", "Pear", "Grape", "Lemon", "Watermelon"); $subset = array_splice($fruits, 2, -1, array("Green Apple", "Red Apple")); print_r($fruits); print_r($subset); // output // Array ( [0] => Apple [1] => Banana [2] => Green Apple [3] => Red Apple [4] => Watermelon ) // Array ( [0] => Orange [1] => Pear [2] => Grape [3] => Lemon ) ?>

You can clearly see how to use this function from the program .

6. The intersection of arrays array_intersect()

array_intersect() The function returns an array of keys , This array consists only of the values that appear in the first array and in every other input array . Its form is as follows ：

array array_intersect(array array1,array array2[,arrayN…])

The following example will return to $fruit1CountGroupinOutpresentOfAndstay$fruit2 and $fruit3 All the fruits that also appear in ：

<?php $fruit1 = array("Apple","Banana","Orange"); $fruit2 = array("Pear","Apple","Grape"); $fruit3 = array("Watermelon","Orange","Apple"); $intersection = array_intersect($fruit1, $fruit2, $fruit3); print_r($intersection); // output // Array ( [0] => Apple ) ?>

Only when two elements are equal and have the same data type ,array_intersect() Functions will think they are the same .

7. Intersection of associative arrays array_intersect_assoc()

function array_intersect_assoc() And array_intersect() Basically the same , But he also considered the keys of the array in the comparison . therefore , Appears only in the first array , And in all other input arrays / Value pairs are returned to the result array .
Form the following ：

array array_intersect_assoc(array array1,array array2[,arrayN…])

The following example returns what appears in $fruit1CountGroupin,alsoSame\; aswhenOutpresentstay$fruit2 And $fruit3 All the keys in / It's worth it ：

<?php $fruit1 = array("red"=>"Apple","yellow"=>"Banana","orange"=>"Orange"); $fruit2 = array("yellow"=>"Pear","red"=>"Apple","purple"=>"Grape"); $fruit3 = array("green"=>"Watermelon","orange"=>"Orange","red"=>"Apple"); $intersection = array_intersect_assoc($fruit1, $fruit2, $fruit3); print_r($intersection); // output // Array ( [red] => Apple ) ?>

8. Difference set of array array_diff()

function array_diff() Returns a value that appears in the first array but not in other input arrays . This function is associated with array_intersect() contrary .

array array_diff(array array1,array array2[,arrayN…])

Examples are as follows ：

<?php $fruit1 = array("Apple","Banana","Orange"); $fruit2 = array("Pear","Apple","Grape"); $fruit3 = array("Watermelon","Orange","Apple"); $intersection = array_diff($fruit1, $fruit2, $fruit3); print_r($intersection); // output // Array ( [1] => Banana ) ?>

9. The difference set of associative arrays array_diff_assoc()

function array_diff_assoc() And array_diff() Basically the same , But it also considers the keys of the array when comparing . therefore , Keys that appear only in the first array and no longer appear in other input arrays / Value pairs are returned to the result array . Its form is as follows ：

array array_diff_assoc(array array1,array array2[,arrayN…])

The following example only returns [yellow] => Banana, Because of this special key / Value pairs appear in $fruit1in,andstay$fruit2 and $fruit3 None of them exist .

<?php $fruit1 = array("red"=>"Apple","yellow"=>"Banana","orange"=>"Orange"); $fruit2 = array("yellow"=>"Pear","red"=>"Apple","purple"=>"Grape"); $fruit3 = array("green"=>"Watermelon","orange"=>"Orange","red"=>"Apple"); $intersection = array_diff_assoc($fruit1, $fruit2, $fruit3); print_r($intersection); // output // Array ( [yellow] => Banana ) ?>

In the process of using an array, you often have to traverse the array . You usually need to traverse the array and get each key or value （ Or get both keys and values ）, So it's no surprise ,PHP For this purpose, some functions are provided to meet the requirements . Many functions can accomplish two tasks , It can not only get the key or value of the current pointer position , It can also move the pointer to the next appropriate position .

10. Gets the current array key key()

key() The function returns input_array The key where the current pointer is located in the . Its form is as follows ：

mixed key(array array)

The following example iterates through the array and moves the pointer to output $fruits The key of the array ：

$fruits=array("apple"=>"red","banana"=>"yellow");while($key = key($fruits)) {
printf("%s
", $key);next($fruits);
}

// apple
// banana

Be careful , Every time you call key() Does not move the pointer . To do this, you need to use next() function , The only purpose of this function is to complete the task of pushing the pointer .

11. Get the current array value current()

current() Function returns the array value of the current pointer in the array . Its form is as follows ：

mixed current(array array)

Let's modify the previous example , This time we're going to get the array value ：

$fruits=array("apple"=>"red","banana"=>"yellow");while($fruit = current($fruits)) {
printf("%s
", $fruit);next($fruits);
}

// red
// yellow

12. Get the current array key and value each()

each() The function returns input_array Current key of / It's worth it , And push the pointer to a position . Its form is as follows ：

array each(array array)

The returned array contains four keys , key 0 and key Contains the key name , And the key 1 and value Contains the corresponding data . If you execute each() The front pointer is at the end of the array , Then return to false.

$fruits=array("apple","banana","orange","pear");prin{t}_r(each($fruits) );

// Array ( [1] => apple [value] => apple [0] => 0 [key] => 0 )

each() Often with list() Used in conjunction with to traverse an array . This example is similar to the previous example , But the loop outputs the entire array ：

$fruits=array("apple","banana","orange","pear");reset($fruits);

while (list($key, $val)=each($fruits))
{
echo “$key => $val
”;
}

// 0 => apple
// 1 => banana
// 2 => orange
// 3 => pear

Because assigning an array to another array will reset the original array pointer , So in the example above, if we were inside the loop, we would $fruits If you assign another variable, it will result in an infinite loop .
This completes the traversal of the array .

lookup 、 Filtering and searching array elements are some common functions of array operations . Let's introduce a few related functions .

13. in_array() function

in_array() Function to search for a specific value in an array , If you find this value, return true, Otherwise return to false. Its form is as follows ：

boolean in_array(mixed needle,array haystack[,boolean strict]);

Let's look at the following example , Find variables apple Whether it is already in the array , If in , Then a message is output ：

$fruit = “apple”;
$fruits=array("apple","banana","orange","pear");if(i{n}_{a}rray($fruit,$fruits))echo"$fruit Already in the array ";

The third parameter is optional , It forces in_array() Consider types when searching .

14. array_key_exists() function

If a specified key is found in an array , function array_key_exists() return true, Otherwise return to false. Its form is as follows ：

boolean array_key_exists(mixed key,array array);

The following example will search in the array key apple, If you find , The color of this fruit will be output ：

$fruit[“apple”] = “red”;
$fruit[“banana”] = “yellow”;
$fruit[“pear”] = “green”;
if(array_key_exists(“apple”, KaTeX parse error: Expected '}', got 'EOF' at end of input: …s color is %s",fruit[“apple”]);
}

//apple’s color is red

15. array_search() function

array_search() Function searches an array for a specified value , If found, the corresponding key is returned , Otherwise return to false. Its form is as follows ：

mixed array_search(mixed needle,array haystack[,boolean strict])

The following example is in $fruits Search for a specific date in （December 7）, If you find , Then return the relevant information of the corresponding state ：

$fruits[“apple”] = “red”;
$fruits[“banana”] = “yellow”;
$fruits[“watermelon”]=“green”;
$founded = array_search(“green”, $fruits);if($founded)
printf("%s was founded on %s.",$founded, $fruits[$founded]);

//watermelon was founded on green.

16. array_keys() function

array_keys() Function returns an array , It contains all the keys found in the searched array . Its form is as follows ：

array array_keys(array array[,mixed search_value])

If optional parameters are included search_value, Then only the key matching the value will be returned . The following example will output $fruit All arrays found in the array ：

$fruits[“apple”] = “red”;
$fruits[“banana”] = “yellow”;
$fruits[“watermelon”]=“green”;
$keys=arra{y}_{k}eys($fruits);
print_r($keys);

//Array ( [0] => apple [1] => banana [2] => watermelon )

17. array_values() function

array_values() Function returns all the values in an array , And automatically provide a numerical index for the returned array . Its form is as follows ：

array array_values(array array)

The following example will get $fruits The value of each element found in ：

$fruits[“apple”] = “red”;
$fruits[“banana”] = “yellow”;
$fruits[“watermelon”]=“green”;
$values=arra{y}_{v}alues($fruits);
print_r($values);

//Array ( [0] => red [1] => yellow [2] => green )

Sometimes we need to extend an array , Or delete part of the array ,PHP Some functions are provided for expanding and shrinking arrays . For those who want to emulate various queue implementations （FIFO、LIFO） For programmers , These functions can provide convenience . seeing the name of a thing one thinks of its function , From the function names of these functions （push、pop、shift and unshift） It clearly reflects its role .

PS： The traditional queue is a data structure , Deleting elements is in the same order as adding elements , It is called first in first out , or FIFO. contrary , Stack is another data structure , The order in which the elements are deleted is the reverse of the order in which they were added , This becomes LIFO , or LIFO.

18. Add element to array header

array_unshift() Function to add an element to the array header . All existing numeric keys will be modified accordingly , To reflect its new position in the array , But the correlation key is not affected . Its form is as follows ：

int array_unshift(array array,mixed variable[,mixed variable])

The following example is in $fruits Two kinds of fruit are added in front of the array ：

$fruits=array("apple","banana");arra{y}_{u}nshift($fruits,“orange”,“pear”)
// $fruits = array(“orange”,“pear”,“apple”,“banana”);

19. Add element at the end of array

array_push() The return value of the function is int type , Is the number of elements in the array after pressing data , You can pass multiple variables as arguments to this function , Push multiple variables into the array at the same time . In the form of ：

(array array,mixed variable [,mixed variable…])

The following example is in $fruits Two more fruits are added to the array ：

$fruits=array("apple","banana");arra{y}_{p}ush($fruits,“orange”,“pear”)
//$fruits = array(“apple”,“banana”,“orange”,“pear”)

20. Delete the value from the array header

array_shift() Function to delete and return the elements found in the array . As a result, , If a numeric key is used , Then all corresponding values will move down , Arrays that use associative keys are not affected . In the form of

mixed array_shift(array array)

The following example deleted $fruits First element in array apple：

$fruits = array(“apple”,“banana”,“orange”,“pear”);
$fruit=arra{y}_{s}hift($fruits);
// $fruits = array(“banana”,“orange”,“pear”)
// $fruit = “apple”;

21. Delete elements from the end of the array

array_pop() The function deletes and returns the last element of the array . In the form of ：

mixed array_pop(aray target_array);

The following example is from $states Array deletes the last state ：

$fruits = array(“apple”,“banana”,“orange”,“pear”);
$fruit=arra{y}_{p}op($fruits);
//$fruits=array("apple","banana","orange");//$fruit = “pear”;