Description:
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When calling DateInterval::createFromDateString() with "6 years and 4 months" as argument, it generates a warning. (See https://3v4l.org/sQjh2)

Note: as a workaround (for the case mentioned) I'm using new \DateInterval('P6Y4M')

Test script:
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<?php

var_dump(\DateInterval::createFromDateString('6 years and 4 months'));


Expected result:
----------------
object(DateInterval)#1 (16) {
    ["y"]=> int(6)
    ["m"]=> int(4)
    ["d"]=> int(0)
    ["h"]=> int(0)
    ["i"]=> int(0)
    ["s"]=> int(0)
    ["f"]=> float(0)
    ["weekday"]=> int(0)
    ["weekday_behavior"]=> int(0)
    ["first_last_day_of"]=> int(0)
    ["invert"]=> int(0)
    ["days"]=> bool(false)
    ["special_type"]=> int(0)
    ["special_amount"]=> int(0)
    ["have_weekday_relative"]=> int(0)
    ["have_special_relative"]=> int(0)
}


Actual result:
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Warning: DateInterval::createFromDateString(): Unknown or bad format (6 years and 4 months) at position 8 (a)