add PHP 8 support

[gregor-j]

Add PHP 8 support.

• Change composer requirement PHP >=7.4
• Switch to PHPUnit 9 and adapt tests and config.
• require PHP_CodeSniffer

[gregor-j]

phpcompatinfo:php-7.2 analyser:run src

Data Source Analysed

Directories                                          1
Files                                                2
Errors                                               0


Extensions Analysis

    Extension Matches REF      EXT min/Max PHP min/Max PHP all 
    Core              Core     5.0.0       5.0.0               
    date              date     5.3.0       5.3.0               
    pcre              pcre     4.0.0       4.0.0               
    standard          standard 4.0.0       4.0.0               
    Total [4]                              5.3.0               

Namespaces Analysis

    Namespace       Matches REF  EXT min/Max PHP min/Max PHP all 
    +global                 Core             5.4.0               
    phpsap\DateTime         user             5.4.0               
    Total [2]                                5.4.0               

No interface found

No trait found

Classes Analysis

    Class                           Matches REF  EXT min/Max PHP min/Max PHP all 
    DateInterval                    1       date 5.3.0       5.3.0               
    DateTime                        1       date 5.2.0       5.2.0               
    parent                          5       Core 5.0.0       5.0.0               
    phpsap\DateTime\SapDateInterval         user             5.4.0               
    phpsap\DateTime\SapDateTime             user             5.2.0               
    static                          1       Core 5.0.0       5.0.0               
    Total [6]                                                5.4.0               

Functions Analysis

    Function   Matches REF      EXT min/Max PHP min/Max  
    preg_match 2       pcre     4.0.0       4.0.0        
    sprintf    2       standard 4.0.0       4.0.0        
    Total [2]                               4.0.0        

Constants Analysis

    Constant  Matches REF  EXT min/Max PHP min/Max  
    false     2       Core 4.0.0       4.0.0        
    null      2       Core 4.0.0       4.0.0        
    Total [2]                          4.0.0        

No condition found

Requires PHP 5.4.0 (min), PHP 5.4.0 (all)