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up vote 1 down vote favorite

I have an array like this.

  $flds = array("fn", "ln", "em");

I have another associative array like this. this is dynamically returned from JSON POST.

  $ret = array("fn" => "xyz", "ln" => "abc", "em" => "s.2", "another" => "123")

I want to search if the first array is existing in the 2nd array. I did this:

  if ( in_array( $flds, array_keys($ret))) 
      echo "exists";
  else 
      echo "does not";

It always returns "does not". When I print, $flds and array_keys($ret), both look exactly same.

Anything wrong here?

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2 Answers

up vote 4 down vote accepted

That code is looking for the entire $flds array to be a value in $ret;

You'll probably want to use array_intersect() and then check the length of the result.

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I took this one. Easier. But wonder why there is no simple search like I wanted, in PHP. Thanks anyways! –  Kevin Rave Jun 7 '12 at 20:39
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up vote 1 down vote

in_array() function searches whether the element is an element of the array. In your case, you want to determine whether the first array is a subset of keys in the second array. Let me show you what works and what does not work:

/* check if 'fn' is an array key key of $ret */
in_array('fn', array_keys($ret)) // true

/* check if array('fn') is an element of array(array('fn'), 'en') */
in_array(array('fn'), array(array('fn'), 'en')) // true

/* check if $flds is a key of $ret */
in_array( $flds, array_keys($ret)) // false

/* check if all elements of $flds are also keys of $ret */
array() === array_diff($flds, array_keys($ret)) // true
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What does the last one return? How do we know all $flds exists or not in $ret? We need to do another condition for count? –  Kevin Rave Jun 7 '12 at 20:27
 
The last one is a boolean comparison. First it creates an array that contains all elements in $flds that are not keys of $ret. Then it checks if this array is empty. –  KSiimson Jun 7 '12 at 20:44
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