PHP makes it relatively easy to build a web-based system, which is much of the reason for its popularity.

Before Debugging PHP That’s Not Working, Consult This List of the 10 Most Common Mistakes That PHP Developers Make.

But its ease of use notwithstanding, PHP has evolved into quite a sophisticated language with many frameworks, nuances, and subtleties that can bite developers, leading to hours of hair-pulling debugging.

This article highlights ten of the more common mistakes that PHP developers need to beware of.


Common Mistake #1: Leaving dangling array references after foreach loops

Common Mistake #2: Misunderstanding isset() behavior

Common Mistake #3: Confusion about returning by reference vs. by value

Common Mistake #4: Performing queries in a loop

Common Mistake #5: Memory usage headfakes and inefficiencies

Common Mistake #6: Ignoring Unicode/UTF-8 issues

Common Mistake #7: Assuming $_POST will always contain your POST data

Common Mistake #8: Thinking that PHP supports a character data type

Common Mistake #9: Ignoring coding standards

Common Mistake #10: Misusing empty()


PHP’s ease of use can lull developers into a false sense of comfort, leaving themselves vulnerable to lengthy PHP debugging due to some of the nuances and idiosyncrasies of the language. This can result in PHP not working and problems such as those described herein.

The PHP language has evolved significantly over the course of its 20 year history. Familiarizing oneself with its subtleties is a worthwhile endeavor, as it will help ensure that the software you produce is more scalable, robust, and maintainable.