php

How do I dynamically write a PHP object property name?

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I have object properties in my code that look like this:

$obj ->field_name_cars[0];
$obj ->field_name_clothes[0];

The problem is I have 100s of field names and need to write the property name dynamically. Otherwise, the object name and the keys for the property will always be the same. So I tried:

$obj -> $field[0];

Hoping that the name of the property would dynamically be changed and access the correct values. But, I keep getting 'undefined property $field in stdClass::$field;

More or less I am trying dynamically write the php before it executes so that it can output the proper values. Thoughts on how to approach this?

Answers

Update for PHP 7.0

PHP 7 introduced changes to how indirect variables and properties are handled at the parser level (see the corresponding RFC for more details). This brings actual behavior closer to expected, and means that in this case $obj->$field[0] will produce the expected result.

In cases where the (now improved) default behavior is undesired, curly braces can still be used to override it as shown below.

Original answer

Write the access like this:

$obj->{$field}[0]

This "enclose with braces" trick is useful in PHP whenever there is ambiguity due to variable variables.

Consider the initial code $obj->$field[0] -- does this mean "access the property whose name is given in $field[0]", or "access the element with key 0 of the property whose name is given in $field"? The braces allow you to be explicit.

Thursday, October 20, 2022

desherkanthaonline-32a87fead484

It works both ways - you need to use the right syntax

//  Non static call
call_user_func( array( $obj, 'method' ) );

//  Static calls
call_user_func( array( 'ClassName', 'method' ) );
call_user_func( 'ClassName::method' ); // (As of PHP 5.2.3)

Wednesday, December 21, 2022

ganpat_kaliya

Here's what worked best for me when trying to script this (in case anyone else comes across this like I did):

$ pecl -d php_suffix=5.6 install <package>
$ pecl uninstall -r <package>

$ pecl -d php_suffix=7.0 install <package>
$ pecl uninstall -r <package>

$ pecl -d php_suffix=7.1 install <package>
$ pecl uninstall -r <package>

The -d php_suffix=<version> piece allows you to set config values at run time vs pre-setting them with pecl config-set. The uninstall -r bit does not actually uninstall it (from the docs):

vagrant@homestead:~$ pecl help uninstall
pecl uninstall [options] [channel/]<package> ...
Uninstalls one or more PEAR packages.  More than one package may be
specified at once.  Prefix with channel name to uninstall from a
channel not in your default channel (pecl.php.net)

Options:
  ...
  -r, --register-only
        do not remove files, only register the packages as not installed
  ...

The uninstall line is necessary otherwise installing it will remove any previously installed version, even if it was for a different PHP version (ex: Installing an extension for PHP 7.0 would remove the 5.6 version if the package was still registered as installed).

Monday, December 12, 2022

shankar_damodaran

You need the parenthesis on the call, like this:

obj[funcName]();

You can get eval to work like this:

eval("obj." + funcName + "()");

but there are many reasons not to do that (security, performance, harder debugging).

Sunday, November 13, 2022

jon_douglas

Never used any of those, but they look interesting..

Take a look at Gearman as well.. more overhead in systems like these but you get other cool stuff :) Guess it depends on your needs ..

Friday, November 11, 2022

the_falvert

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