PHP String strspn() Function

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The PHP String strspn() function is used to determine the length of the first segment of a string inserted inside another string. In simple terms, the strspn() function allows us to determine "how many characters are present within another string?" It returns the total number of characters found in the string that only contains the characters.

It is a case-sensitive function that treats uppercase and lowercase letters differently.

Syntax

Below is the syntax of the PHP String strspn() function −

int strspn(
   string $string,
   string $characters,
   int $offset = 0,
   ?int $length = null
)

Parameters

Here are the parameters of the strspn() function −

• $string − (Required) It is the String handle returned by String_init().

• $characters − (Optional) It is the specific information field you want to retrieve.

• $offset − (Optional) It is the specific information field you want to retrieve.

• $length − (Optional) It is the specific information field you want to retrieve.

If offset and length are missing, the entire string will be examined. If they are included, the result will be the same as executing strspn(substr($string, $offset, $length), $characters) .

Return Value

The strspn() function returns the length of the first segment of a string that includes entirely of characters.

Note: When the offset parameter is set, the returned length is calculated from this place rather than the beginning of the string.

PHP Version

First introduced in core PHP 4, the strspn() function continues to function easily in PHP 5, PHP 7, and PHP 8.

Example 1

Here is the basic example of the PHP String strspn() function to get the first segment of a string.

<?php
   echo strspn("tutorialspoint","t");
?>

Output

Here is the outcome of the following code −

1

Example 2

In the below PHP code uses the strspn() function to check the length of initial characters in the given string that match a set of allowed characters.

<?php
   // Define string here
   $string = "1234abc";
   $allowedCharacters = "1234567890";

   // Find the length of the initial numeric characters
   $length = strspn($string, $allowedCharacters);

   // Print the result
   echo "The length of initial numeric characters is: $length\n";
?> 

Output

This will generate the below output −

The length of initial numeric characters is: 4

Example 3

This program shows the use of the offset parameter inside the strspn() function to start the search from a given position.

<?php
   // Define string here
   $string = "hello123world456";
   $allowedCharacters = "1234567890";
   
   // Start after the word 'hello'
   $offset = 5; 

   // Find the length starting from position 5
   $length = strspn($string, $allowedCharacters, $offset);

   // Output the result
   echo "The length of numeric characters starting at offset $offset is: $length\n";
?> 

Output

This will create the below output −

The length of numeric characters starting at offset 5 is: 3

Example 4

In this example we are using both offset and length parameters in the strspn() function. And we will specify a substring by offset and length to search within.

<?php
   // Define string here
   $string = "php12345example";
   $allowedCharacters = "1234567890";
   
   // Start from '1'
   $offset = 3;  
   
   // Check only the next 5 characters
   $lengthToSearch = 5; 

   // Find the length of numeric characters 
   $length = strspn($string, $allowedCharacters, $offset, $lengthToSearch);

   // Output the result
   echo "The length of numeric characters within the specified substring is: $length\n";
?> 

Output

Following is the output of the above code −

The length of numeric characters within the specified substring is: 5