PHP linter: make the path to the executable configurable

Fixes #1388

ale_linters/php/php.vim

@@ -1,6 +1,8 @@
 " Author: Spencer Wood <https://github.com/scwood>, Adriaan Zonnenberg <amz@adriaan.xyz>
 " Description: This file adds support for checking PHP with php-cli
 
+call ale#Set('php_php_executable', 'php')
+
 function! ale_linters#php#php#Handle(buffer, lines) abort
     " Matches patterns like the following:
     "
@@ -30,8 +32,8 @@ endfunction
 
 call ale#linter#Define('php', {
 \   'name': 'php',
-\   'executable': 'php',
+\   'executable_callback': ale#VarFunc('php_php_executable'),
 \   'output_stream': 'stdout',
-\   'command': 'php -l -d error_reporting=E_ALL -d display_errors=1 -d log_errors=0 --',
+\   'command': '%e -l -d error_reporting=E_ALL -d display_errors=1 -d log_errors=0 --',
 \   'callback': 'ale_linters#php#php#Handle',
 \})

doc/ale-php.txt

@@ -203,5 +203,15 @@ g:ale_php_cs_fixer_options                          *g:ale_php_cs_fixer_options*
 
   This variable can be set to pass additional options to php-cs-fixer.
 
+===============================================================================
+php                                                                *ale-php-php*
+
+g:ale_php_php_executable                              *g:ale_php_php_executable*
+                                                      *b:ale_php_php_executable*
+  Type: |String|
+  Default: `'php'`
+
+  This variable sets the executable used for php.
+
 ===============================================================================
   vim:tw=78:ts=2:sts=2:sw=2:ft=help:norl:

doc/ale.txt

@@ -224,6 +224,7 @@ CONTENTS                                                         *ale-contents*
       phpstan.............................|ale-php-phpstan|
       psalm...............................|ale-php-psalm|
       php-cs-fixer........................|ale-php-php-cs-fixer|
+      php.................................|ale-php-php|
     po....................................|ale-po-options|
       write-good..........................|ale-po-write-good|
     pod...................................|ale-pod-options|

test/command_callback/test_php_command_callback.vader

@@ -0,0 +1,14 @@
+Before:
+  call ale#assert#SetUpLinterTest('php', 'php')
+  let b:command_tail = ' -l -d error_reporting=E_ALL -d display_errors=1'
+  \   . ' -d log_errors=0 --'
+
+After:
+  call ale#assert#TearDownLinterTest()
+
+Execute(The executable should be configurable):
+  AssertLinter 'php',  ale#Escape('php') . b:command_tail
+
+  let b:ale_php_php_executable = '/path/to/php'
+
+  AssertLinter '/path/to/php', ale#Escape('/path/to/php') . b:command_tail