php - Accessing arrays whitout quoting the key -

i can access array value either $array[key] or $array['key']

is there reason avoid using 1 on other?

use latter variant $array['key']. former work because php tolerant , assumes string value key if there no constant named key:

always use quotes around string literal array index. example, $foo['bar'] correct, while $foo[bar] not. […] wrong, works. reason […] has undefined constant (bar) rather string ('bar' - notice quotes).

see array do's , don'ts.

now in opposite accessing arrays in plain php code, when using variable parsing in double quoted strings need write without quotes or use curly brace syntax:

[…] inside double-quoted string, it's valid not surround array indexes quotes "$foo[bar]" valid. see above examples details on why section on variable parsing in strings.

so:

// syntax error echo "$array['key']";  // valid echo "$array[key]"; echo "{$array['key']}";