Similarities and differences between the two ways of merging two arrays

This article discusses two ways to combine arrays: $a + $b, array_merge ($a, $b)

operator +, insert the last array on the basis of the previous number, if there is the same discard, and Array_merge is the first argument based on the insertion of the latter parameter, if there is the same key used after an overlay. Examples are as follows:

php > $a = array (' A ' = ' 1 ', ' b ' = ' 2 ', ' c ' = ' 3 ');p hp > $b = Array (' C ' =>3, ' d ' = ' 4 ', ' e ' = ' 5 ');p hp > $c = $a + $b;p hp > $d = Array_merge ($a, $b);p hp > Var_dump ($c, $d), Array (5) {  ' a ' + =  string (1) "1"  B ' + =  string (1) "2"  ' C ' and "= =  string (1)" 3 "  ' d ' = = =  String (1)" 4 "  ' e ' = =  string (1 ) "5"}array (5) {  ' a ' + =  string (1) "1"  ' b ' = +  string (1) "2"  ' C ' + =  int (3)  ' d ' +  string (1) "4"  ' e ' + =  string (1) "5"}php > $e = Array_merge ($b, $a);p hp > Var_dump ($e); Array (5) {  ' c ' + =  string (1) "3"  ' d ' + =  string (1) "4"  ' e ' = +  string (1) "5"  ' a ' and ' =  string (1) ' 1 ' ' b ' and ' = '  string (1) ' 2 '}php > $f = $b + $a;p hp > Var_dump ($f), Array (5) {  ' c ' + =  int (3)  ' d ' and ' +  string (1) "4"  ' e ' = =  string (1) "5"  ' a ' + =  String (1) "1"  ' b ' = =  string (1) "2"}

When both sides are indexed arrays, using array_merge may cause an index reset, as in the following scenario:

php > $a = array ();p hp > $b = Array (1=> ' data ');p hp > $c = $a + $b;p hp > $d = Array_merge ($a, $b);p hp > Var_ Dump ($c, $d); Array (1) {  [1] = =  string (4) "Data"}array (1) {  [0] = =  string (4) "Data"}

Therefore, when using + to merge two indexed arrays, the values may be discarded, and array_merge will not, resetting the duplicate index:

php > $a = array (1=> ' one ',2=> ', ',3=> ' three ');p hp > $b = Array (3=> ' three ',4=> ' four ',5=> ' five ' );p hp > $c = $a + $b;p hp > $d = Array_merge ($a, $b);p hp > Var_dump ($c, $d); Array (5) {  [1] =  string (3) "on E "  [2] = =  string (3)" ""  [3] = =  string (5) "Three"  [4] = =  string (4) "Four"  [5] = >  String (4) "Five"}array (6) {  [0] = =  string (3) "One"  [1] and  string (3) "One"  [2 ] = =  string (5) "Three"  [3]  = = string (5) "Three"  [4] = =  string (4) "Four"  [5] = >  String (4) "Five"}

Similarities and differences between the two ways of merging two arrays