PHP Find Array Value Program_PHP Tutorial-PHP Tutorial-php.cn

PHP Find Array Value Program_PHP Tutorial

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Release： 2016-07-13 17:14:41

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There are many ways to find a specified value in an array in php. Below I will introduce the usage of array search functions in_array(), array_key_exists(), array_search() in php

To find whether an element is in an array, there are a total of The above three methods:

in_array 'Function searches for a given value in an array. in_array(value,array,type)type optional. If this parameter is set to true, it is checked whether the type of the searched data and the value of the array are the same.

array_key_exists 'array_key_exists() function determines whether the specified key exists in an array. If the key exists, it returns true, otherwise it returns false. array_key_exists(key,array)

Example #1 array_key_exists() example

The code is as follows

代码如下	复制代码
$search_array = array('first' => 1, 'second' => 4); if (array_key_exists('first', $search_array)) { echo "The 'first' element is in the array"; } ?>

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$search_array = array('first' => 1, 'second' => 4);

代码如下

复制代码

$search_array = array('first' => null, 'second' => 4);

// returns false
isset($search_array['first']);

// returns true
array_key_exists('first', $search_array);
?>

if (array_key_exists('first', $search_array)) {

echo "The 'first' element is in the array";
}

代码如下

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$a=array("a"=>"Dog","b"=>"Cat","c"=>"Horse");
echo array_search("Dog",$a);
?>

$a=array("a"=>"5","b"=>5,"c"=>"5");
echo array_search(5,$a,true);
?>
上述代码将输出下面的结果：
b

Example #2 Comparison between array_key_exists() and isset()

isset() does not return TRUE for NULL values in the array, while array_key_exists() does.

The code is as follows

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$search_array = array('first' => null, 'second' => 4);

// returns false

isset($search_array['first']);

// returns true

array_key_exists('first', $search_array);

代码如下	复制代码
$result = array(); for($i = 501; $i < 600; $i++) { if(!isset($arr[$i])) continue; $result[] = $arr[$i]; }

mixed array_search ( mixed $needle, array $haystack [, bool $strict] ) The first parameter is the value to be searched, the second parameter is the array, and the last parameter refers to whether to check whether the data types are the same when searching.

The code is as follows

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$a=array("a"=>"Dog","b"=>"Cat","c"=>"Horse"); echo array_search("Dog",$a); ?> $a=array("a"=>"5","b"=>5,"c"=>"5"); echo array_search(5,$a,true); ?> The above code will output the following results: b From this point of view, when the amount of data is not large, such as less than 1,000, any search method can be used, and it will not become a bottleneck; When the amount of data is relatively large, array_key_exists is more appropriate. Of course, the memory occupied by array_key_exists here is relatively large. According to calculations The array structures are: array(1, 2, 3, ..) and array(1 => true, 2 => false, ..) Their memory usage ratio is 1:2; Note: array_key_exist is more than ten or even dozens of times more efficient than in_array A simple algorithm Assume that the array has 1000 elements and the key values are unordered positive integers less than 1000000 and are not continuous, as follows $arr = array(1 => 'sadas', 20 => 'aasd', 5002 => 'fghfg', 190023 => 'rty', 248 => 'kj', 76 = > 'sddd' ,...); Now we want to get the elements whose key value in array $arr is greater than 500 and less than 600. Is there a more efficient algorithm without using foreach to completely loop? Answer

The code is as follows

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$result = array(); for($i = 501; $i < 600; $i++) { If(!isset($arr[$i])) continue; $result[] = $arr[$i]; }