fix #6 compatibility with psr 1.2.0

[remicollet]

Using php 8.0.13 and psr 1.2.0

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TEST RESULT SUMMARY
---------------------------------------------------------------------
Exts skipped    :    0
Exts tested     :   17
---------------------------------------------------------------------

Number of tests :  196               196
Tests skipped   :    0 (  0.0%) --------
Tests warned    :    0 (  0.0%) (  0.0%)
Tests failed    :    0 (  0.0%) (  0.0%)
Tests passed    :  196 (100.0%) (100.0%)
---------------------------------------------------------------------
Time taken      :    1 seconds
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