The way PHP determines whether a string exists in an array element

Method One: Adopt In_array (Value,array,type)

Type is optional. If this parameter is set to True, the search data is checked for the same type as the value of the array.

. The code is as follows:

$arr = Array (' Can ', ' how ', ' method ', ' Know ', ' no ', ' no ');

In_array (Value,array,type)

$isin = In_array ("How 2", $arr);

if ($isin) {

echo "in====". $isin;

}else{

echo "out====". $isin;

}

Method Two:

The Array_key_exists ' array_key_exists () function determines whether a specified key exists in an array, returns TRUE if the key exists, or returns false. Array_key_exists (Key,array

Method Three:

The Array_search () function, like In_array (), looks for a key value in the array. If the value is found, the key name of the matching element is returned. Returns False if it is not found. Array_search (value,array,strict), when the amount of data is relatively large, with array_key_exists more appropriate, but the memory is larger,

The array structure is: Array (1, 2, 3, ...) and Array (1 => true, 2 => false, ...), memory usage ratio is 1:2.

Specifically related to internal implementation, in PHP, the first and second type of data structure is similar, are associative arrays.

Other supplements:

There are three ways to find whether an element is in an array:

The In_array ' function searches the array for a given value. In_array (value,array,type) type is optional. If this parameter is set to True, the search data is checked for the same type as the value of the array.

The Array_key_exists ' array_key_exists () function determines whether a specified key exists in an array, returns TRUE if the key exists, or returns false.

Array_key_exists (Key,array)

The Array_search ' Array_search () function, like In_array (), looks for a key value in the array. If the value is found, the key name of the matching element is returned. Returns False if it is not found.

Array_search (value,array,strict)

From this point of view, when the amount of data is small, such as less than 1000, to find which one is OK, will not become a bottleneck;

When the amount of data is larger, it is more appropriate to use array_key_exists.

Of course, here array_key_exists occupy a larger memory, after the calculation

The array structure is: Array (1, 2, 3, ...) and Array (1 => true, 2 => false, ...)

Their memory usage ratio is 1:2;

This is related to the internal implementation, which is actually similar to the first and second data structures in PHP, and is an associative array.