phpcs.xml

<?xml version="1.0"?>
<ruleset name="PHP_CodeSniffer">
    <description>PHP Code Sniffer configuration file.</description>
    <!-- https://github.com/squizlabs/PHP_CodeSniffer -->

    <!-- check all these dirs/files -->
    <file>app</file>
    <file>bin</file>
    <file>cfg</file>
    <file>src</file>

    <!-- but don't check these -->
    <exclude-pattern>composer$</exclude-pattern>
    <exclude-pattern>public$</exclude-pattern>

    <!-- phpcs argument options -->
    <arg name="basepath" value="./"/>
    <arg name="colors"/>
    <arg name="tab-width" value="4"/>
    <arg name="extensions" value="php,js,css"/>
    <!-- how many files to check at once -->
    <arg name="parallel" value="10"/>

    <!-- base rule: set to PSR12-->
    <!-- https://www.php-fig.org/psr/psr-12/ -->
    <!-- https://github.com/squizlabs/PHP_CodeSniffer/wiki/Customisable-Sniff-Properties -->
    <rule ref="PSR12">
		<!-- add any exclusions here -->
    </rule>

    <!-- Don't hide tokenizer exceptions -->
    <rule ref="Internal.Tokenizer.Exception">
        <type>error</type>
    </rule>

    <!-- require 4 spaces, css -->
    <rule ref="Squiz.CSS.Indentation">
        <properties>
            <property name="indent" value="4" />
        </properties>
    </rule>

    <!-- lines can be lineLimit chars long (warnings), errors at absoluteLineLimit chars -->
    <rule ref="Generic.Files.LineLength">
        <properties>
            <!-- 120 is PSR12; cannot be 0; large for sql, arrays -->
            <property name="lineLimit" value="360"/>
            <!-- 0 to not show as error -->
            <property name="absoluteLineLimit" value="0"/>
        </properties>
    </rule>

    <!-- ban some functions -->
    <rule ref="Generic.PHP.ForbiddenFunctions">
        <properties>
            <property name="forbiddenFunctions" type="array">
                <element key="sizeof" value="count"/>
                <element key="delete" value="unset"/>
                <element key="print" value="echo"/>
                <element key="is_null" value="null"/>
                <element key="create_function" value="null"/>
            </property>
        </properties>
    </rule>

</ruleset>

Example PHP CodeSniffer phpcs.xml using PSR12 as a base rule, plus adding in app dirs, excluding some shared libs/dirs, and some rules exclusions due to app.