php nextint PHP官方手册 – 互联网笔记

php nextint PHP官方手册 – 互联网笔记

Order of when using a loop:

1. the first of the loop,::() is .

2. each of the loopphp nextint, ::valid() is .

3a. It ::valid() false,the loop is .

3b. If ::valid() truephp nextintphp nextint,::() and

::key() are .

4. The loop body is .

5. After each of the loopphp nextint PHP官方手册 – 互联网笔记, ::next() is and we from step 2 above.

This is to:

The loop isn’t until ::valid() false or the body of the loop a break .

The only two that are are ::() and ::valid() ( an ).

The ::next() need not . It is as void. On the other hand, it is for this to , in which case you can do so if you want.

If your is doing , like a query and over the set,the best place to make the query is in the ::() .

In this casephp nextint PHP官方手册 – 互联网笔记, the of the can be cheap, and after you can to set the of the query all the way up to the of the loop since the

::() isn’t until then.

to keep in mind when a set :

* Make sure you close your or clean up any query at the top of the . your code will break if the same is used in two loops when the first loop with a break all the are over.

* Make sure your () tries to grab the first so that the call to valid() will know or not the set is empty. I do this by next() from the end of my () .

* For like set , there isn’t a “key” that you can , you know you have a key in the query. ,there will be cases where the doesn’t know the key it isn’t the query, the of the query is such that a key isn’t , the is over a table that doesn’t have one, or the is over a table that has a key. In these cases, key() can :

the row index (based on a that you ), or can null.

can also be used to:

* over the lines of a file or rows of a CSV file

* over the of a

* over the in an input

* over the by an xpath

* over the by a

* over the files in a

* etc…