In shared hosting environments, such as those provided by Brixly, the 'Select PHP Version' screen often displays a default PHP memory_limit value that is lower than the maximum available. This article explains the rationale behind setting a lower default memory_limit, the implications of increasing it, and the limitations faced by resellers in adjusting this default value.

Why a Lower Default PHP Memory Limit is Recommended: 

The PHP memory_limit setting controls the maximum amount of memory that a script is allowed to allocate. It acts as a safeguard, preventing any single script from consuming all available server resources, which could lead to server instability and poor performance for other users on the same server.

By default, Brixly sets a conservative memory_limit to ensure that all users on a shared server have access to the necessary resources and to maintain overall server health. This conservative limit is sufficient for the majority of websites and applications under typical usage scenarios.

Scaling PHP Memory Limit: 

It is recommended to increase the PHP memory_limit only when necessary, such as when a site is consistently hitting its memory limit, which could be indicated by errors in the site's logs or slow performance. Incremental adjustments allow for careful monitoring of the impact on server resources.

For example, a WordPress site with a default memory_limit of 128M may function well under normal conditions. However, during a traffic surge or when running a resource-intensive plugin, the site may require an increase to 256M to handle the additional load without errors.

Reseller Limitations and Shared Hosting Stability: 

Resellers do not have the capability to set the default PHP memory_limit across their hosting accounts. This limitation is in place to prevent the inadvertent allocation of excessive memory to individual accounts, which could compromise server performance and stability.

In a shared hosting environment, if multiple users were to increase their memory_limit to the maximum of 1GB, the cumulative effect could exhaust server resources, leading to slow performance, increased load times, and even server crashes. This would negatively impact all users on the server. Whilst this is absolutely fine for sites that require it, setting it across the entire server can, and would have a negative impact to others, including your own clients. 

 Understanding PHP Threads and Memory Allocation in LVE / CloudLinux Environments:

PHP Threads and Execution: 

PHP threads refer to individual units of execution running within the web server. Each time a PHP script is executed, it runs in a single thread within the server's process. In a shared hosting environment, multiple PHP threads may be running simultaneously, each serving different requests from various users.

PHP Memory_Limit vs. LVE RAM Limit: 

The PHP memory_limit is a specific setting within the PHP configuration that dictates the maximum amount of memory a PHP script can consume during its execution. This limit is set to prevent a single PHP script from using too much memory, which could potentially affect the performance of other scripts running on the server.

On the other hand, the RAM (Memory) limit included as part of CloudLinux's LVE settings is a broader restriction that applies to all processes running under a specific user account. This includes not just PHP scripts, but also other applications and processes initiated by the user. The LVE RAM limit ensures that each user on a shared server can only consume a certain amount of the server's total memory, thus preventing any single account from monopolizing the server's resources.

For example, suppose a user's LVE RAM limit is set to 2GB. In that case, all processes combined under that user's account, including multiple PHP threads, databases, and scheduled tasks, must operate within this 2GB limit. However, each PHP script initiated by the user will also be subject to the PHP memory_limit, which might be set to a lower value, such as 128MB, to further control the memory usage at the script level.

By having both PHP memory_limit and LVE RAM limits, Brixly ensures a balanced resource allocation that promotes stability and performance across all hosted accounts. It's important to note that while users can adjust the PHP memory_limit within their cPanel, the LVE RAM limits are predefined by the hosting plan and can only be increased by upgrading to a higher-tier plan.

Conclusion: The default PHP memory_limit is set to a lower value to ensure a balanced distribution of resources in a shared hosting environment. While Brixly allows users to increase their memory_limit as needed, it is essential to do so judiciously and only when justified by the application's requirements. Resellers should be aware of the potential impact on server stability when modifying PHP settings and adhere to best practices to maintain optimal performance for all users. PHP memory_limit and LVE RAM limits work together to manage memory allocation efficiently in a shared hosting environment. PHP memory_limit controls the memory usage per script, while LVE RAM limits govern the total memory usage per user account, both playing crucial roles in maintaining server stability and performance.