PHP 5.6报错：Cannot use [] for reading 请帮忙排查原因

Hey there! Let's break down why that fatal error is popping up with your code. The line in question looks simple enough, but there's a sneaky, easy-to-miss culprit here:

• Hidden Unicode characters are almost certainly the issue
  That => arrow followed by [] might look clean at first glance, but there's probably an invisible control character (like a zero-width space) tucked right between them. PHP 5.6 is far less forgiving of these unprintable characters than newer PHP versions, so it throws a fatal error when it can't parse the code correctly.

• How to fix it step by step

  1. Fire up your code editor and enable the "show invisible characters" feature (most modern editors like VS Code have this under settings—look for options like "Render Control Characters"). You’ll likely spot a tiny, odd-looking character right before the empty array [].
  2. Delete that hidden character, then manually re-type the => [] portion of the line. Don’t copy-paste the original code, since that might carry over the invisible character again.
  3. Test with a minimal script to confirm. Run this super simple snippet first:

     <?php
     $fieldDefinitions = ['first_name' => []];
     var_dump($fieldDefinitions);
     

     If this runs without errors, you’ll know the original problem was definitely that hidden character.

• A quick syntax check to rule out the obvious
  Just to be thorough: PHP 5.6 fully supports the short array syntax [], so that’s not causing the error here. The issue is purely a parsing failure from that unexpected hidden character.

内容的提问来源于stack exchange，提问作者JorgeeFG