Kit.Lester wrote: > Trying to learn PHP *well*, I've bogged down on table 15-5 in > http://www.php.net/manual/en/language.operators.comparison.php - it claims to > describe comparisons between different types, but then has a lot of missing > combinations, some internal clashes, a few bits which leave me in doubt, and > then *does* cover most of the same-type comparisons at various levels of > explicitness.
I'm the author of the table, thanks for your interest. The main point to understand the table is read it from top to bottom (and not try to find the proper line at first sight). Operands are tested for the type in this order. Knowing this fact, you will find that every possible combination is listed. > TABLE 15-5 CLAIMS IT IS FOR "DIFFERENT" OPERAND TYPES "Different" should be "various". I've fixed it in CVS. > -- implicitly might be covering bool vs bool array vs array > leaving only null vs null uncovered... :-) null vs null is covered on the line "bool or null vs anything". > QUERIES IN THE TABLE: > -- "numeric or lexic comparison" presimably means that if both strings are > numeric, they are cast to numeric and compared -- but (1) what is a > "numeric" string? - one that starts with + - or a digit, so that trailing > non-numeric data is ignored? so "115 Somestreet"=="115 Anotherstreet"? > (2) what of the case where only one string is "numeric"? Numeric string consists of digits only and optional plus/minus and optional decimal point. You can test it with is_numeric(). > -- does array-vs-anything cover array-vs-array? isn't a-vs-a special? array vs array has its own line. > CLASHES (i.e. appear twice): > -- null op string > -- string op string (assume the explicit string vs string overrides the > string-etc vs string etc?) > -- does reources resource cast to numeric? oris that excluded from that > entry? or does it matter? I hope that with the "read the table from top to bottom" fact is everything clear. E.g. string vs string is matched on the first line of course, 4th line matches s-n, s-r, n-s, r-s, n-n, r-r, n-r, r-n. Jakub Vrana
