Exclusive to PHP 7.4 - Read-only

Question

Exclusive to PHP 7.4 - Read-only

I developed a PHP library that utilizes the PHP 8.0 readonly keyword, but now I want to ensure compatibility with earlier versions like 7.4.

Although it would be simple to remove the readonly keywords from my code, I believe they serve an important purpose and don't want to discard them.

As someone with a background in C, I considered using macros, but unfortunately, PHP does not support them. I came across this answer which suggests a method for implementing macro-like behavior, but it seems excessive, especially considering my library consists of 26 files.

Is there a straightforward way to have PHP 7.4 ignore the readonly keyword in order to create cross-version compatible code? Something similar to this hypothetical C code snippet:

#if PHP_VERSION < 8
#define readonly /**/
#enif

Perhaps there exists a composer build option that could preprocess files before packaging them?

php readonly version-compatibility

Answer 1

Answer №1

By default, PHP does not support the type of conditional compilation you are looking for.

One approach could be to preprocess the source files dynamically, utilizing a custom autoloader or Composer hook. The concept is to allow the normal code to execute until it reaches the point where it would typically include the file, then intercept its content and adjust it as needed.

It's important to note that this doesn't have to function like a complete macro system; rather, you can simply enclose the code with clear markers like

/* IF PHP 8 */ readonly /* END IF */

and use a basic regex pattern to identify and modify them:

$php_code = file_get_contents($php_file_being_loaded);
if ( PHP_VERSION_ID < 80000 ) {
    $php_code = preg_replace('#/\* IF PHP 8 \*/.*?/\* END IF \*/#s', '', $php_code);
}
eval($php_code);

Alternatively, you could perform the preprocessing "offline" to generate separate versions of the library automatically: one for PHP 8.0 and higher, and another for PHP 7.4. This process could be straightforward like the previous method, or you could utilize a tool such as Rector, which analyzes and rewrites standard PHP code without additional markers based on predefined rules, including converting it to match a specific PHP version.

Answer 2

By default, PHP does not support the type of conditional compilation you are looking for.

One approach could be to preprocess the source files dynamically, utilizing a custom autoloader or Composer hook. The concept is to allow the normal code to execute until it reaches the point where it would typically include the file, then intercept its content and adjust it as needed.

It's important to note that this doesn't have to function like a complete macro system; rather, you can simply enclose the code with clear markers like

/* IF PHP 8 */ readonly /* END IF */

and use a basic regex pattern to identify and modify them:

$php_code = file_get_contents($php_file_being_loaded);
if ( PHP_VERSION_ID < 80000 ) {
    $php_code = preg_replace('#/\* IF PHP 8 \*/.*?/\* END IF \*/#s', '', $php_code);
}
eval($php_code);

Alternatively, you could perform the preprocessing "offline" to generate separate versions of the library automatically: one for PHP 8.0 and higher, and another for PHP 7.4. This process could be straightforward like the previous method, or you could utilize a tool such as Rector, which analyzes and rewrites standard PHP code without additional markers based on predefined rules, including converting it to match a specific PHP version.

Answer 3

Answer №2

PHP does not involve compilation, hence compiler macros are not applicable.
Referencing the Backward Incompatible Changes, a new keyword has been introduced:

readonly is now a reserved keyword. However, it can still be used as a function name.

You have two options: a) refrain from re-assigning its value or b) manage two versions simultaneously.

Answer 4

PHP does not involve compilation, hence compiler macros are not applicable.
Referencing the Backward Incompatible Changes, a new keyword has been introduced:

readonly is now a reserved keyword. However, it can still be used as a function name.

You have two options: a) refrain from re-assigning its value or b) manage two versions simultaneously.

Answer 5

Answer №3

Many frameworks opt to steer clear of utilizing modern features for this very reason (such as WordPress, Symfony, Laravel). However, if you are determined, your best solution may lie with Composer, allowing you to have a v1.x.x version with composer.json

{
    "require": {
        "php": ">=7.4"
    },
}

as well as a v2.x.x version with composer.json

{
    "require": {
        "php": ">=8.0"
    },
}

By doing composer require lib, Composer will automatically search and install the latest version of your library that is compatible with the local php version and composer.json constraints (-:

The drawback is that you'll need to maintain both v1 and v2 of your library for as long as you wish to support php 7.4 though..

Another approach is to have a loader like lib.php

if(PHP_MAJOR_VERSION >= 8){
    require("lib_modern.php");
} else{
    require("lib_legacy.php");
}

yet again, requiring maintenance for both lib_modern and lib_legacy.

Answer 6

Many frameworks opt to steer clear of utilizing modern features for this very reason (such as WordPress, Symfony, Laravel). However, if you are determined, your best solution may lie with Composer, allowing you to have a v1.x.x version with composer.json

{
    "require": {
        "php": ">=7.4"
    },
}

as well as a v2.x.x version with composer.json

{
    "require": {
        "php": ">=8.0"
    },
}

By doing composer require lib, Composer will automatically search and install the latest version of your library that is compatible with the local php version and composer.json constraints (-:

The drawback is that you'll need to maintain both v1 and v2 of your library for as long as you wish to support php 7.4 though..

Another approach is to have a loader like lib.php

if(PHP_MAJOR_VERSION >= 8){
    require("lib_modern.php");
} else{
    require("lib_legacy.php");
}

yet again, requiring maintenance for both lib_modern and lib_legacy.

Exclusive to PHP 7.4 - Read-only

Answer №1

Answer №2

Answer №3

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