PHP substr_count() Function

The PHP substr_count() function returns the number of occurrences of specified substring in the specified string.

Note: The substring is case-sensitive. This function doesn't count overlapped substrings (see the example below).

Syntax

substr_count(string, substring, offset, length)

Parameters

`string`	`Required.` Specify the input string.
`substring`	`Required.` Specify the substring to search for.
`offset`	`Optional.` Specify offset parameter which indicates where to start counting in the string. If it is negative, counting starts from the end of the string.
`length`	`Optional.` Specify the maximum length after the specified offset to search for the substring. It generates a warning if the offset plus the length is greater than the string length. A negative length counts from the end of string.

Return Value

Returns the number of occurrences of substring in the string.

Example:

In the example below, this function is used to find out the number of occurrences of given substring in the given string.

<?php
$str = "This is an island.";

//number of occurrences of 'is' in the string
echo "1. ".substr_count($str, 'is')."\n"; 

//the string is reduced to 's is an island.'
//therefore returns 2
echo "2. ".substr_count($str, 'is', 3)."\n"; 

//the string is reduced to 's an island.'
//therefore returns 1
echo "3. ".substr_count($str, 'is', 6)."\n"; 

//the string is reduced to 's i'
//therefore returns 0
echo "4. ".substr_count($str, 'is', 3, 3)."\n"; 
?>

The output of the above code will be:

1. 3
2. 2
3. 1
4. 0

Example:

Consider the example below which illustrates on function behavior with overlapped substrings. The function doesn't count overlapped substrings.

<?php
$str = "ABCABCABC";

//number of occurrences of 'ABCABC' in the string
echo substr_count($str, 'ABCABC'); 
?>

The output of the above code will be:

Example:

When the offset plus the length parameter is greater than the string length, the function generates a warning. Consider the example below.

<?php
$str = "ABCABCABC";

//string length
echo "string length: ".strlen($str)."\n";

//generates a warning because 3+10 > 9
echo substr_count($str, 'ABCABC', 3, 10); 
?>

The output of the above code will be:

string length: 9

PHP Fatal error:  Uncaught ValueError: substr_count(): Argument #4 ($length) must be contained in argument #1 ($haystack) in Main.php:8
Stack trace:
#0 Main.php(8): substr_count()
#1 {main}
  thrown in Main.php on line 8

❮ PHP String Reference