Details of comparison operators

body{font:12px Arial;margin:3px;overflow-y:auto;overflow-x:auto}p{margin:0px;}blockquote, ol, ul{margin-top:0px;margin-bottom:0px;} Hi! 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've been sorting out other doubts about the language by writing test scripts, but this  would  need to many  tests to be  practical:  so the help of someone already familiar with this would be appreciated. Also, the results could be useful to others in the community. SO - the table  below is my best  interpretation  of 15-5, plus some  notes on explicit  doubts.  Assistance  in  completing/correcting  the  table  would be appreciated! -- Kit Lester [You'll need to view the following in a fixed width font.]          | null | boolean ! string     | res'ce or | array ! object          !      !         !            ! numeric   !       ! ---------+------+---------+------------+-----------+-------+------------ null     | same |         ! casts null |           !       !          |      |         ! to ""      |           !       ! ---------+------+---------+------------+-----------+-------+------------ null     | same ! cast both operands to boolean, then FALSE<TRUE ---------+------+---------+------------+-----------+-------+------------ boolean  | convert operand 2 to boolean then FALSE<TRUE ---------+------+---------+------------+-----------+-------+------------ string   !      !         ! numeric or !          !      !         ! lexic      !          !      !         ! compare ?? ! ---------+------+---------+------------+-----------+-------+------------ string   |      !         ! cast str   | cast str  |       ! resource |      !         ! /res to    ! /res to   !       ! or       |      !         ! numeric,   ! numeric,  !       ! numeric  |      !         ! then       ! then      !       !          !      !         ! "usual"    ! "usual"   !       ! ---------+------+---------+------------+-----------+-------+------------ array    ! array 1st operand is always greater (except ar vs ar???) ---------+------+---------+------------+-----------+-------+------------ object   ! object 1st operand is always greater            ! PHP4 != PHP5 ---------+------+---------+------------+-----------+-------+------------ TABLE 15-5 CLAIMS IT IS FOR "DIFFERENT" OPERAND TYPES  -- but then  explicity  covers  string  vs string  (twice?),  str/res/num  vs     str/res/num and obj vs obj  -- implicitly might be covering bool vs bool array vs array leaving only null vs null uncovered... :-) 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"?  -- does array-vs-anything cover array-vs-array? isn't a-vs-a special? 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? LOTTA GAPS... Lycos email has now 300 Megabytes of free storage... Get it now at mail.lycos.co.uk