Memory Limits

Learning Focus

By the end of this lesson you will know how to set PHP memory limits correctly based on application behavior, not guesswork.

What memory_limit Does

The PHP memory_limit setting controls the maximum memory a single PHP process can use. If a script exceeds this limit, PHP kills it with a fatal error.

Setting Memory Limits

# Find your php.ini location
/usr/local/lsws/lsphp84/bin/lsphp --ini

# Edit php.ini
sudo nano /usr/local/lsws/lsphp84/etc/php/8.4/litespeed/php.ini

; Set memory limit
memory_limit = 256M

Sizing Guidelines

Application Type	Recommended	Rationale
Simple custom PHP	64-128 MB	Lightweight scripts
WordPress (basic)	128-256 MB	Plugins increase memory usage
WordPress (heavy plugins)	256-512 MB	Page builders, WooCommerce
Laravel / Symfony	128-256 MB	Framework overhead

The RAM Formula

Total PHP memory = Workers × memory_limit

Example: 15 workers × 256 MB = 3.84 GB reserved for PHP

Ensure this fits within your server's available RAM alongside OpenLiteSpeed, the OS, and any databases.

warning

Setting memory_limit too high without checking total worker count can cause the server to swap, which is worse than a single PHP script failing. Always calculate the total.

Checking Current Usage

# Check memory usage per lsphp worker
ps aux | grep lsphp | awk '{print $6/1024 " MB  PID: " $2}'

# Check total PHP memory usage
ps aux | grep lsphp | awk '{sum += $6} END {print "Total: " sum/1024 " MB"}'

Key Takeaways

• Set memory_limit based on measured application needs, not maximum values.
• Always calculate Workers × memory_limit to ensure it fits in available RAM.
• Monitor actual usage to find the right balance.

What's Next

• Continue to Process Limits for PHP worker pool sizing.