Php array filter functions: array_filter and array_unique

In php, I will introduce two commonly used array filter functions, array_filter and array_unique. One is to filter array null values and the other is to filter array repeated values. Let's take a look at them now.

Syntax
Array_filter (array, function)
Parameter description
Array is required. Specifies the input array.
The name of a function. If it is null, all elements with flase values are filtered out.

The Code is as follows:

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<? Php Function odd ($ var ){ Return ($ var & 1 ); } Function even ($ var ){ Return (! ($ Var & 1 )); } $ Array1 = array ("a" => 1, "B" => 2, "c" => 3, "d" => 4, "e" => 5 ); $ Array2 = array (6, 7, 8, 9, 10, 11, 12 ); Echo "Odd: n "; Print_r (array_filter ($ array1, "odd ")); Echo "Even: n "; Print_r (array_filter ($ array2, "even ")); /* Odd: Array ( [A] => 1 [C] => 3 [E] => 5 ) Even: Array ( [0] => 6 [2] => 8 [4] => 10 [6] => 12 ) */

Filter out repeated values in the PHP Array

To remove duplicate values from an array, you can use the foreach method or the array_unique method. The following code uses both methods.

The Code is as follows:

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<? Php $ ArrF = array (); $ ArrS = array (); $ IntTotal = 100; $ IntRand = 10; For ($ I = 0; $ I <$ intTotal; $ I ++) { $ ArrF [] = rand (1, $ intRand ); $ ArrS [] = rand (1, $ intRand ); } $ ArrT = array_merge ($ arrF, $ arrS ); $ ArrRF = array (); $ IntStart = time (); Foreach ($ arrT as $ v) { If (in_array ($ v, $ arrRF )) { Continue; } Else { $ ArrRF [] = $ v; } } $ IntEnd = time (); $ IntTime = $ intEnd-$ intStart; Echo "With Continue, Spend time: $ intTime <br/> "; $ IntStart1 = time (); $ ArrRS = array_unique ($ arrT ); $ IntEnd2 = time (); $ IntTime2 = $ intEnd2-$ intStart1; Echo "With array_unique function, Spend time :( $ intTime2 )"; Echo "<pre> "; Print_r ($ arrT ); Print_r ($ arrRF ); Print_r ($ arrRS ); Echo "</pre> "; ?>

When $ intTotal is relatively small, for example, the value of $ intRand within 1000 basically does not affect the result, and the execution time of both is similar.

When the value of $ intTotal is greater than 10000 and $ intRand is set to 100, the efficiency of using array_unique is higher than that of foreach loop judgment. $ intRand = 10, the execution time of the two is the same.

Therefore, it can be concluded that when the array capacity is small and it is about 1000 or less, the execution efficiency of the two is almost the same.

When the array capacity is relatively large (the specific value is not tested in detail, you can determine the value if you are interested), as $ intRand increases, array_unique performs better, I don't use the $ intTotal/$ intRand ratio because it doesn't feel proportional, but the larger the ratio, the better the array_unique performance.

To sum up, we recommend that you use array_unuique when filtering array duplicate values. When the array is not large, the efficiency of the two is the same, while the use of array_unique will of course reduce your code by several lines at once, function performance is better when the array capacity is too large

Two-dimensional array deduplication Function

PHP array deduplication has a built-in function array_unique (), but the php array_unique function is only applicable to one-dimensional arrays and not to multidimensional arrays. The following provides a two-dimensional array array_unique Function

The Code is as follows:

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Function unique_arr ($ array2D, $ stkeep = false, $ ndformat = true) { // Determine whether the primary array key is retained (the primary array key can be non-numeric) If ($ stkeep) $ stArr = array_keys ($ array2D ); // Determine whether the secondary array key is retained (all secondary array keys must be the same) If ($ ndformat) $ ndArr = array_keys (end ($ array2D )); // Dimensionality reduction. You can also use implode to convert a one-dimensional array to a string connected with commas (,). Foreach ($ array2D as $ v ){ $ V = join (",", $ v ); $ Temp [] = $ v; } // Remove the duplicate string, that is, the duplicate one-dimensional array. $ Temp = array_unique ($ temp ); // Re-assemble the split Array Foreach ($ temp as $ k => $ v) { If ($ stkeep) $ k = $ stArr [$ k]; If ($ ndformat) { $ TempArr = explode (",", $ v ); Foreach ($ tempArr as $ ndkey => $ ndval) $ output [$ k] [$ ndArr [$ ndkey] = $ ndval; } Else $ output [$ k] = explode (",", $ v ); } Return $ output; } Test $ Array2D = array ('first' => array ('title' => '123', 'date' => '123 '), 'second' => array ('title' => '123', 'date' => '123 '), 'third' => array ('title' => '123456', 'date' => '123456 ')); Print_r ($ array2D ); Print_r (unique_arr ($ array2D, true ));