Seven Lesser‑Known PHP Built‑in Functions and How to Use Them

PHP provides a large number of built‑in functions, many of which are widely used, while some remain hidden in the corners of the language yet offer great utility; this article showcases seven such functions.

1. highlight_string() – Useful for displaying PHP code with syntax highlighting. It returns or outputs a highlighted version of the supplied code.

<?php
  highlight_string('<?php phpinfo(); ?>');
?>

2. str_word_count() – Returns the number of words in a string when passed a string argument.

<?php
  $str = "How many words do I have?";
  echo str_word_count($str); // Outputs 6
?>

3. levenshtein() – Calculates the Levenshtein (edit) distance between two strings, useful for detecting misspellings.

<?php
  $str1 = "carrot";
  $str2 = "carrrott";
  echo levenshtein($str1, $str2); // Outputs 2
?>

4. get_defined_vars() – Returns a multidimensional array containing all defined variables, including environment, server, and user‑defined variables.

print_r(get_defined_vars());
// Array ( [_GET] => Array ( ) [_POST] => Array ( ) [_COOKIE] => Array ( ) [_FILES] => Array ( ) )

5. escapeshellcmd() – Escapes special characters in a string to prevent command‑injection attacks; often used together with exec() or system().

<?php
  $command = './configure ' . $_POST['configure_options'];
  $escaped_command = escapeshellcmd($command);
  system($escaped_command);
?>

6. checkdate() – Validates a Gregorian date; returns true for valid dates and false otherwise.

<?php
  var_dump(checkdate(12, 31, 2000)); // bool(true)
  var_dump(checkdate(2, 29, 2001));  // bool(false)
?>

7. php_strip_whitespace() – Returns the source code of a file with comments and whitespace removed, useful for comparing code size versus comments.

<?php
  // PHP comment here
  /*
   * Another PHP comment
   */
  echo php_strip_whitespace(__FILE__);
  // Newlines are considered whitespace, and are removed too:
  do_nothing();
?>

These functions expand the toolbox of PHP developers, offering concise solutions for syntax highlighting, word counting, fuzzy string matching, variable inspection, command safety, date validation, and code size analysis.