A program that PHP merges the values of 2 numeric key arrays

First you need to understand a basic knowledge point

Two arrays in PHP can be combined with + or array_merge, but there is a difference, and if you don't know the difference, it's going to kill you!
The main difference is that if the same key name appears in two or more arrays, the key name is divided into strings or numbers, which requires attention
1 when the key name is a number, the value following the Array_merge () will not overwrite the original value, but append to the back, but the + merge array will return the first occurrence of the value as the final result, and those values that have the same key name in the following array "Discard" (not overwrite)
2 when the key name is a string, Array_merge () overrides the value of the same key name in front of it, but the + still returns the first occurrence of the value as the final result, and those values that have the same key name in the following array are "discarded" (not overwritten).

The code is as follows

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$a = Array (' A ', ' B '); $b = Array (' C ', ' d '); $c = $a + $b; Var_dump ($a); Var_dump (Array_merge ($a, $b)); Output: Array 0 => string ' a ' (length=1) 1 => string ' B ' (length=1) Array 0 => string ' a ' (length=1) 1 => string ' B ' (length=1) 2 => string ' C ' (length=1) 3 => string ' d ' (length=1) ++++++++++++++++++++++++++++++++++++++++++ $a = Array ( 0 => ' a ', 1 => ' B ' ); $b = Array ( 0 => ' C ', 1 => ' B ' ); $c = $a + $b; Var_dump ($c); Var_dump (Array_merge ($a, $b)); Output: Array 0 => string ' a ' (length=1) 1 => string ' B ' (length=1) Array 0 => string ' a ' (length=1) 1 => string ' B ' (length=1) 2 => string ' C ' (length=1) 3 => string ' B ' (length=1) ++++++++++++++++++++++++++++++++++++++++++ $a = Array (' A ', ' B '); $b = Array ( ' 0 ' => ' C ', 1 => ' B ' ); $c = $a + $b; Var_dump ($c); Var_dump (Array_merge ($a, $b)); Output: Array 0 => string ' a ' (length=1) 1 => string ' B ' (length=1) Array 0 => string ' a ' (length=1) 1 => string ' B ' (length=1) 2 => string ' C ' (length=1) 3 => string ' B ' (length=1) ++++++++++++++++++++++++++++++++++++++++++ $a = Array ( 0 => ' a ', 1 => ' B ' ); $b = Array ( ' 0 ' => ' C ', ' 1 ' => ' B ' ); $c = $a + $b; Var_dump ($c); Var_dump (Array_merge ($a, $b)); Output: Array 0 => string ' a ' (length=1) 1 => string ' B ' (length=1) Array 0 => string ' a ' (length=1) 1 => string ' B ' (length=1) 2 => string ' C ' (length=1) 3 => string ' B ' (length=1)

All right, so much for you. Let's take a look at the value of merging 2 numeric key arrays

The code is as follows

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<?php /** * PHP merges the values of 2 numeric key arrays * * @param array $arr 1 * @param array $arr 2 * @return Array * @author www.111cn.net */ function New_array_merge ($arr 1, $arr 2) { $arr = Array_flip ($arr 1) + Array_flip ($arr 2); Return Array_keys ($arr); } $arr 1 = array (' AA ', ' BB ', ' cc '); $arr 2 = Array (' Aa2 ', ' BB ', ' cc2 '); $arr = New_array_merge ($arr 1, $arr 2); Print_r ($arr); Output: Array ( [0] => AA [1] => BB [2] => cc [3] => Aa2 [4] => CC2 )