PHP string operation

String related operations

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1. Single and double quotation marks define the string

The contents of double quotation marks are PHP The analytic result is ; Single quotation marks are WYSIWYG

<?php
$test="PHP";
$str1="I Like $test";
$str2='I Like $test';
echo $str1;
echo "<br>";
echo $str2;
?>
//I Like PHP
//I Like $test

2. String manipulation

2.1 Remove leading and trailing spaces and special characters

（1）trim() function

Used to remove white space characters at the beginning and end of a string ( Or other characters )

trim(string str,string charlist)

str String object for operation ,charlist Is an optional parameter , Characters you want to filter . If you don't specify the character , Then the following characters are taken by default .

Parameter values	explain
\0	null
\t	tab, tabs
\n	A newline
\x0B	Vertical tabs
\r	A carriage return
“ ”	Space

（2）ltrim() function

Remove the characters on the left side of the string

ltrim(string str,string charlist)

（2）rtrim() function

Remove the characters on the right side of the string

rtrim(string str,string charlist)

<?php
$str='$I Like PHP.html$';
echo trim($str,'$');
echo"<br>";
echo ltrim($str,'$');
echo"<br>";
echo rtrim($str,'$');
?>
<!--I Like PHP.html
I Like PHP.html$
$I Like PHP.html-->

2.2 Gets the length of the string

strlen(string str)

Output the specified string length

<?php
$str2='I Like PHP';
echo strlen($str2);
?>
//12

$notesIt\; means$： Chinese characters take up two characters , Others account for 1 Characters

2.3 Intercepting string

substr(string str,int start,int length)

Parameters	explain
str	Specify string object
start	Specify where to start intercepting the string . if start It's a negative number , Then intercept from the end
length	Specify the number of intercepted strings , It's a negative number , Then the penultimate length character string

<?php
$str='ILikePHP';
echo substr($str,0);
echo"<br>";
echo substr($str,1,7);
echo"<br>";
echo substr($str,-4,4);
?>
//ILikePHP
//LikePHP
//ePHP

2.4 Retrieve string

1.strstr() function

Gets the substring from the first occurrence of the specified string in another string to the end of the latter

strstr(string haystack,string needle)

Parameters	explain
haystack	Necessary parameters , Specified string
needle	Specify the characters , If it is a numerical value, it corresponds to ASCII Value matches character

<?php
$str='ILikePHP.html';
echo strstr($str,'.');
?>
//.html Get file suffix 

2. substr_count() function

Returns the number of occurrences of the retrieval string

substr_count(string haystack,string needle)

<?php
$str='ILikePHP.html';
echo substr_count($str,'P');
?>
//2

2.5 Replace string

Implement the replacement of the specified string

1.str_ireplace() function

Replace the original string with the new substring. The string specified to be replaced

str_ireplace(mixed search,mixed replace,mixed subject,int count)

Parameters	explain
search	Value to search , It can be used array Provide multiple values
replace	Specify the replacement value
subject	String or array searched and replaced
count	Optional parameters , Number of replacements performed

<?php
$str1="P";
$str2="*";
$str='I Like PHP.html';
echo str_ireplace($str1,$str2,$str);
?>
<!--I Like *H*.html-->

2. substr_replace() function

substr_replace(mixed string,mixed repl,mixed start,mixed length)

<?php
$str1="***";
$str='I Like PHP.html';
$count = 3;
echo substr_replace($str,$str1,7,$count);
?>

<!--I Like ***.html-->

2.6 Division 、 Composite string

1. explode() function

explode(string delimiter,string str ,int limit)

<?php
$str='I Like PHP.html';
$str_arr=explode(' ',$str);
print_r($str_arr);
echo "<br>";
echo $str_arr[0];
echo "<br>";
echo $str_arr[1];
echo "<br>";
echo $str_arr[2];
?>
<!--Array ( [0] => I [1] => Like [2] => PHP.html )
I
Like
PHP.html-->

2. implode() function

implode (string glue,array pieces)

<?php
$str='I Like PHP.html';
$str_arr=explode(' ',$str);
print_r($str_arr);
echo"<br>";
echo implode(" ",$str_arr)
?>
<!--Array ( [0] => I [1] => Like [2] => PHP.html )
I Like PHP.html-->