PHP inverse array and permutation array key and value explanation

PHP inverse array and permutation array keys and values

Inverse array element order

The Array_reverse () function resets the order of the elements in the array. The form is as follows:

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Array array_reverse (array array [, Boolean Preserve_keys])

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If the optional parameter Preserve_keys is set to true, the key mapping is persisted. Otherwise, the re-placed values will correspond to the first

The corresponding key z in the previous position

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$states = Array ("Delaware", "Pennsylvania", "New Jersey");p Rint_r (Array_reverse ($states));//Array ([0] = new Jerse y [1] = Pennsylvania [2] = Delaware)

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Can be compared with the results obtained when Preserve_keys is enabled

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$states = Array ("Delaware", "Pennsylvania", "New Jersey");p Rint_r (Array_reverse ($states, 1));//Array ([2] = new Je Rsey [1] = Pennsylvania [0] = Delaware)

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Arrays that use associative keys are unaffected by Preserve_keys, and the key mappings are always maintained for associative arrays.

Permutation array keys and values

The ARRAY_FL IP () function displaces the role of the keys and their corresponding values in the array. The form is as follows Z

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Array array_flip (array array)

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Here is an example of this function Z

$state = Array ("Delaware", "Pennsylvania", "New Jersey"), $state = Array_flip ($state);p rint_r ($state);

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This example returns the following result Z

Array ([Delaware] = 0 [pennsylvania].=> 1 [New Jersey] + 2)

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