function::strpos - Linux


The strpos function is a PHP function that searches for the first occurrence of a string within another string and returns the index of the first character of the found string. It is primarily used for string manipulation tasks like finding substrings, validating inputs, and performing text-based operations.


int strpos(string $haystack, string $needle, int $offset = 0)


  • $haystack: The string to search within.
  • $needle: The substring to search for.
  • $offset: (Optional) The offset to start searching from. Defaults to 0, indicating the start of the string.


// Find the position of "PHP" in the string
echo strpos("This is a PHP script", "PHP"); // Output: 19

// Search for "language" starting from position 10
echo strpos("PHP is a popular programming language", "language", 10); // Output: 30

// Check if a substring exists
if (strpos("Hello world", "universe") !== false) {
    echo "The substring 'universe' exists.";

Common Issues

  • Index not found: If the substring is not found, the function returns false instead of an index.
  • Invalid search parameters: Make sure the input parameters are valid strings.
  • Offset out of bounds: Ensure the $offset parameter is within the range of the $haystack.


strpos can be combined with other string functions like substr and str_replace for advanced string manipulation tasks. For example:

// Extract a substring from the index of the found string
$position = strpos($haystack, $needle);
if ($position !== false) {
    $substring = substr($haystack, $position);

Related Commands

  • preg_match: Performs regular expression pattern matching in a string.
  • str_replace: Replaces occurrences of a substring with another string.
  • substr: Extracts a portion of a string based on specified indices.