Detailed explanation of deleting elements in arrays in PHP (unset, array_splice) Summary of additions and deletions of array elements

Deleting array elements in

is very simple, mainlyunset and array_splice. However, if they are used together for a long time, sometimes they cannot tell the difference. Today I specially summarize it to increase memory and make it easier to use.

The difference is like this in many placesunset,array_splice

If the array_splice() function is deleted, the index value of the array will also change.
If the unset() function is deleted, the index value of the array will not change.

In fact, I think there is a prerequisite for such a distinction.

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$arr0=array('a','b','c','d','f'); $arr1=array( 'name'=>'lidequan', 'tel'=>'131****1234', 'height'=>'175', 'weight'=>'65' ); $arr2=array( 1=>'lidequan', 3=>'131****1234', 4=>'175', 6=>'65' ); $arr3=array( 'a'=>'lidequan', 3=>'131****1234', 4=>'175', 10=>'1705', 'b'=>'65' ); //1. array_splice($arr0,2,1); //2. unset($arr0[2]); //3. array_splice($arr1,2,1); //4. unset($arr1['height']); //5. array_splice($arr2,2,1); //6. unset($arr1[4]); //7.array_splice($arr3,2,1);

The execution results of 1 and 2 are different

1 Execution result:

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array (size=4) 0 => string 'a' (length=1) 1 => string 'b' (length=1) 2 => string 'd' (length=1) 3 => string 'f' (length=1)

2 Execution result:

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array (size=4) 0 => string 'a' (length=1) 1 => string 'b' (length=1) 3 => string 'd' (length=1) 4 => string 'f' (length=1)

The execution results of 3 and 4 are the same

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array (size=3) 'name' => string 'lidequan' (length=8) 'tel' => string '131****1234' (length=11) 'weight' => string '65' (length=2)

The execution results of 5 and 6 are different

The execution results of 5 are as follows

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array (size=3) 0 => string 'lidequan' (length=8) 1 => string '131****1234' (length=11) 2 => string '65' (length=2)

6 The execution results are as follows:

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array (size=3) 1 => string 'lidequan' (length=8) 3 => string '131****1234' (length=11) 6 => string '65' (length=2) 7的执行结果如下：

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array (size=4) 'a' => string 'lidequan' (length=8) 0 => string '131****1234' (length=11) 1 => string '1705' (length=4) 'b' => string '65' (length=2)

总结：这说明，unset,array_splice，在删除数组元素，数组索引值变化原理在于

unset函数是按照数组键值进行删除数组里面的元素，删除之后，不再对数组进行任何操作。

array_splice函数删除元素是依据元素在数组中的次序（次序从0开始算起），进行删除元素，删除元素之后，如果数组中存在键值为整数的元素，将这些元素，依据其在数组中次序大小，将其键值从0~n依次更新。

补充：

关于数组添加删除元素操作

1.从头开始添加元素

array_unshift($a,"blue");

2.从尾添加元素 array_push()

array_push($a,"blue");

$a[]='blue';

3.从头开始删除元素

array_unshift($a);

4.从尾开始删除元素

array_pop($a);

5.删除指定位置的元素

array_splice($a,2,1);

6.删除指定键值的元素

unset($a[2]);

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