PHP foreach value by reference

Mike Milano — July 1, 2008 - 10:49pm

The best way to demonstrate this is to establish an objective.

Objective: Write a function to capitalize all elements of an array.

There's at least 3 general ways we could go about this but obviously I'd like to show you how this can be accomplished using foreach with the value of each iteration as a reference.

<?php
 
function capitalizeArray($array) {
  // make sure input is an array, and return an array if it isn't just to be nice.
  if (!is_array($array)) {
    return array();
  }
 
  // create a foreach structure with '&' before the value to access it as a reference
  foreach ($array as &$value) {
 
    // set $value t uppercase
    $value = strtoupper($value);
 
  }
 
  // return the array
  return $array();
}
?>

Notice we did not need to access the original array with a key to change the values inside of it. i.e. $array[0] = strtoupper($array[0]);

Remember that this will not work in PHP4 so don't use it if your code needs to be backwards compatible.

Thank you very much for this

Anonymous (not verified) — January 28, 2011 - 7:56am

Thank you very much for this tutorial. It's been rather helpful. I only wanted to emphasize readers' attention on the thing that when using foreach to pass an array's key ($key => $value), the key must be a string and not binary content - containing 0's, f.e., as was my case when i used foreach to parse bencoded data handed back to me from a bittorrent tracker scraping - as this will throw foreach off and hand you a key that is binary different than the actual content of the array.

Thank you very much for this

Anonymous (not verified) — January 28, 2011 - 7:38am

Thank you very much for this tutorial. It's been rather helpful. I only wanted to emphasize readers' attention on the thing that when using to pass an array's key ($key => $value), the key must be a string and not binary content - containing 0's, f.e., as was my case when i used foreach to parse bencoded data handed back to me from a bittorrent tracker scraping - as this will throw foreach off and hand you a key that is binary different than the actual content of the array.