How to find a string in an array in PHP?

Question

I have an array:

$array = array("apple", "banana", "cap", "dog", etc..) up to 80 values.

and a string variable:

$str = "abc";

If I want to check whether this string ($str) exists in the array or not, I use the preg_match function, which is like this:

$isExists = preg_match("/$str/", $array);

if ($isExists) {
    echo "It exists";
} else {
    echo "It does not exist";
}

Is it the correct way? If the array grows bigger, will it be very slow? Is there any other method? I am trying to scaling down my database traffic.

And if I have two or more strings to compare, how can I do that?

can use two function in_array() and array_search() Plaese see the tutorial prepared by me braincybersolutions.com/php-tutorial/php-search-in-array — Syam K S - SEO Specialist
– Syam K S - SEO Specialist, Commented May 2, 2013 at 14:34

htoip · Accepted Answer · 2012-07-03 01:45:58Z

36

 bool in_array  ( mixed $needle  , array $haystack  [, bool $strict  ] )

http://php.net/manual/en/function.in-array.php

edited Jul 3, 2012 at 1:45

htoip

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answered Feb 17, 2009 at 8:49

Sam McAfee

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Comments

Paul Dixon · Accepted Answer · 2009-02-17 09:17:19Z

If you just need an exact match, use in_array($str, $array) - it will be faster.

Another approach would be to use an associative array with your strings as the key, which should be logarithmically faster. Doubt you'll see a huge difference between that and the linear search approach with just 80 elements though.

If you do need a pattern match, then you'll need to loop over the array elements to use preg_match.

You edited the question to ask "what if you want to check for several strings?" - you'll need to loop over those strings, but you can stop as soon as you don't get a match...

$find=array("foo", "bar");
$found=count($find)>0; //ensure found is initialised as false when no terms
foreach($find as $term)
{
   if(!in_array($term, $array))
   {
        $found=false;
        break;
   }
}

carbin · Accepted Answer · 2009-02-17 09:00:32Z

5

preg_match expects a string input not an array. If you use the method you described you will receive:

Warning: preg_match() expects parameter 2 to be string, array given in LOCATION on line X

You want in_array:

if ( in_array ( $str , $array ) ) {
    echo 'It exists';
} else {
    echo 'Does not exist';
}

answered Feb 17, 2009 at 9:00

carbin

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1 Comment

roa3 Over a year ago

the string like this $var "id1;id2";

JohnnyPark · Accepted Answer · 2009-02-17 08:52:02Z

3

Why not use the built-in function in_array? (http://www.php.net/in_array)

preg_match will only work when looking for a substring in another string. (source)

answered Feb 17, 2009 at 8:52

JohnnyPark

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Comments

Gumbo · Accepted Answer · 2009-02-17 09:16:32Z

2

If you have more than one value you could either test every value separatly:

if (in_array($str1, $array) && in_array($str2, $array) && in_array($str3, $array) /* … */) {
    // every string is element of the array
    // replace AND operator (`&&`) by OR operator (`||`) to check
    // if at least one of the strings is element of the array
}

Or you could do an intersection of both the strings and the array:

$strings = array($str1, $str2, $str3, /* … */);
if (count(array_intersect($strings, $array)) == count($strings)) {
    // every string is element of the array
    // remove "== count($strings)" to check if at least one of the strings is element
    // of the array
}

answered Feb 17, 2009 at 9:16

Gumbo

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Comments

MissionNext · Accepted Answer · 2016-05-12 17:17:35Z

0

The function in_array() only detects complete entries if an array element. If you wish to detect a partial string within an array, each element must be inspected.

foreach ($array AS $this_string) {
  if (preg_match("/(!)/", $this_string)) {
    echo "It exists"; 
  }
}

answered May 12, 2016 at 17:17

MissionNext

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