php - xPath, DomDocument, Scraping table -

this question has answer here:

• why xpath query (scraping html tables) work in firebug, not application i'm developing? 2 answers

i have link need scraping using xpath , domdocument on table. need to name of chemmical, link , part. i've tried using xpath helper in chrome no luck, doesn't make right query. ideas i'm doing wrong? i'm using query: //table/tbody/tr/td/a

i able data looking using xpath helper in chrome in following manner (these lines typed chrome console):

all chemicals / first chemical:

> allchemicals = $x("descendant::tr/td[(position() =1)]") > firstchemical = allchemicals[0].innertext 

all links / first link:

> alllinks = $x("descendant::tr/td[(position() =1)]/a") > firstlink = alllinks[0].href 

all parts / first part:

> allparts = $x("descendant::tr/td[(position() =2)]") > firstpart = allparts[0].innertext 

hope helps.