Invalid argument supplied for foreach()

php foreach
Roberto Aloi picture Roberto Aloi · Apr 13, 2010 · Viewed 848.5k times · Source

It often happens to me to handle data that can be either an array or a null variable and to feed some foreach with these data.

$values = get_values();

foreach ($values as $value){
  ...
}

When you feed a foreach with data that are not an array, you get a warning:

Warning: Invalid argument supplied for foreach() in [...]

Assuming it's not possible to refactor the get_values() function to always return an array (backward compatibility, not available source code, whatever other reason), I'm wondering which is the cleanest and most efficient way to avoid these warnings:

  • Casting $values to array
  • Initializing $values to array
  • Wrapping the foreach with an if
  • Other (please suggest)

Answer

Andy Shellam picture Andy Shellam · Apr 13, 2010

Personally I find this to be the most clean - not sure if it's the most efficient, mind!

if (is_array($values) || is_object($values))
{
    foreach ($values as $value)
    {
        ...
    }
}

The reason for my preference is it doesn't allocate an empty array when you've got nothing to begin with anyway.

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