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Professional Information Technology-Programming Book part 69

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Tham khảo tài liệu 'professional information technology-programming book part 69', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Multidimensional Arrays It is possibleand often very usefulto use arrays to store two-dimensional or even multidimensional data. Accessing Two-Dimensional Data In fact a two-dimensional array is an array of arrays. Suppose you were to use an array to store the average monthly temperature by year using two key dimensionsthe month and the year. You might display the average temperature from February 1995 as follows echo temps 1995 feb Because temps is an array of arrays temps 19 95 is an array of temperatures indexed by month and you can reference its elements by adding the key name in square brackets. Defining a Multidimensional Array Defining a multidimensional array is fairly straightforward as long as you remember that what you are working with is actually an array that contains more arrays. You can initialize values by using references to the individual elements as follows temps 1995 feb 41 You can also define multidimensional arrays by nesting the array function in the appropriate places. The following example defines the first few months for three years the full array would clearly be much larger than this temps array 1995 array jan 36 feb 42 mar 51 1996 array jan 37 feb 42 mar 49 1997 array jan 34 feb 40 mar 50 The print_r function can follow as many dimensions as an array contains and the formatted output will be indented to make each level of the hierarchy readable. The following is the output from the three-dimensional temps array just defined Array 1995 Array jan 36 feb 42 mar 51 1996 Array jan 37 feb 42 mar 49 1997 Array jan 34 feb 40 mar 50 Summary In this lesson you have learned how to create arrays of data and manipulate them. The next lesson examines how regular expressions are used to perform pattern matching on strings. Summary In this lesson you have learned how to create arrays of data and manipulate them. The next lesson examines how regular expressions are used to perform pattern matching on .