PHP string strcmp() Function

String comparison is one of the most common tasks in programming and development. strcmp() is a string comparison function in PHP. It is a built-in function of PHP, which is case sensitive, means it treats capital and the small case separately. It is used to compare two strings from each other. This function compares two strings and tells whether a string is greater, less, or equal to another string. strcmp() function is binary safe string comparison.

Note: strcmp() function is case sensitive as well as binary safe string comparison.

Syntax:

Parameters

strcmp() function accepts two strings parameter, which is mandatory to pass in the function body. Both parameters are mandatory to pass in strcmp() function(). Description of the following parameters is given below.

$str1 - It is the first parameter of strcmp() function that is used in the comparison.
$str2 - It is the second parameter of strcmp() function to be used in the comparison.

Value return by strcmp()

This function returns integer value randomly based on the comparison.

Return 0 - It returns 0 if both strings are equal, i.e., $str1 = $str2

Return < 0 - It returns negative value if string1 is less than string2, i.e., $str1 < $str2

Return >0 - It returns positive value if string1 is greater than string 2, i.e., $str1 > $str2

Note: It calculates ASCII value of the string and then compares both strings to check that they are equal, greater or less from each other.

Difference between strcoll() and strcmp() functions

strcoll() and strcmp() both are string comparison function of PHP, but they slightly differ with each other.

Strcoll() takes the bytes and transform them using locale, then compares the result, whereas, strcmp() takes the bytes of string one by one and then compares them whatever the bytes are.

Example 1

<?php
	$str1 = "hello php";
	$str2 = "hello php";
	echo strcoll($str1, $str2). " because both strings are equal. ";
	echo " </br>";
	echo strcoll("Hello world", "Hello"). " because the first string is greater than the second string.";
?>

Output:

0 because both strings are equal. 
6 because the first string is greater than the second string.

Remark: Second string comparison has returned the value 6 because the first string is greater than the second string by 6 characters, including whitespace.

Example 2

<?php
	echo strcoll("Hello world", "hello"). " because the first string is less than the second string.";
	echo "</br>";	
	echo strcoll("hello", "Hello"). " because the first string is greater than the second string.";
?>

Output:

-1 because the first string is less than the second string.
1 because the first string is greater than the second string.

Example 3

<?php
	echo strcmp("Hello ", "HELLO").  " because the first string is greater than the  second string.";
	echo "</br>";	
	echo strcmp("Hello world", "Hello world Hello"). " because the first string is less than the second string.";
?>

Output:

1 because the first string is greater than the second string.
-6  because the first string is less than the second string.

Remark: Second string comparison has returned -6 because the first string is 6 characters smaller than the second string, including whitespace.

String1	String2	Output	Explanation
Hello	Hello	0	Both strings are same and equal.
Hello	hello	-1	String1 < String2 because ASCII value of H is 72 and h is 104 so that H < h. It treats the small and capital letters differently.
hello	Hello	1	String1 > String2 because ASCII value of H is 72 and h is 104 so that H < h.
Hello PHP	Hello	4	String1 > String2 because of String1 greater than String2 by 6 characters including whitespace.
hello	Hello PHP	1	String1 > String2 because ASCII value of H is 72 and h is 104 so that H < h.
Hello	Hello PHP	-4	String1 < String2 because String1 is lesser than String2 by 4 characters including whitespace.