It shows array_push as undefined function even in some basic code.
To Reproduce
<?php
$tmp = [];
$tmp2 = [];
$tmp2[] = 'aaa';
array_push($tmp, $tmp2);
Expected behavior
it shows as defined function
Screenshots

Platform and version
Windows VSCODE, remote SSH to Debian, version 1.3.3
Have you changed intelephense.stubs setting?
Have you changed
intelephense.stubssetting?
No, for example array_merge is working without problems

Somebody set array_push as @since 7.3... https://github.com/JetBrains/phpstorm-stubs/blob/534dac2ac3b2e853298d52f29a339c17fb70ba91/standard/standard_8.php#L1018
Will work if you set 7.3 or higher
"intelephense.environment.phpVersion": "7.3.0"
Made PR https://github.com/JetBrains/phpstorm-stubs/pull/713
Wow! Nice find @KapitanOczywisty
Merged may be closed.
Most helpful comment
Somebody set
array_pushas@since 7.3... https://github.com/JetBrains/phpstorm-stubs/blob/534dac2ac3b2e853298d52f29a339c17fb70ba91/standard/standard_8.php#L1018Will work if you set 7.3 or higher
"intelephense.environment.phpVersion": "7.3.0"Made PR https://github.com/JetBrains/phpstorm-stubs/pull/713