You may make mistakes in php array operations...

1. is the key name an error caused by quotation marks: & amp; lt ;? Php $ array = array (3 = & amp; gt; & quot; number & quot;, '3' = & amp; gt; & quot; character & quot ;); echo $ arra

1. whether the key name contains quotation marks:

 "Number", '3' => "character"); echo $ array [3]; // character echo $ array ['3']; // character

The former is the value of the fourth element, and the latter is the value of the element whose return key name is 3.

2. string value:

 
The character in the string can be searched and modified using a square brackets similar to the array structure containing the corresponding numbers, such as $ str [42], you can think of strings as arrays. Of course, you can modify the value of a character in the string.