v3.23.1

Summary of significant accounting policies (Details) | 12 Months Ended
--- | ---
Jan. 31, 2023 USD ($) segment processor | Jan. 31, 2022 USD ($) | Jan. 31, 2021 USD ($)
Accounting Policies [Line Items] |  |  |
Settlement period (in days) | 2 days |  |
Number of third party payment processors | processor | 1 |  |
Advertising expense | $ 2,634,000 | $ 4,007,000 | $ 558,000
Allowance for doubtful accounts | 1,053,000 | 863,000 | 699,000
Asset impairment charges | $ 0 | $ 0 | $ 0
Number of operating segment | segment | 1 |  |
ESPP |  |  |
Accounting Policies [Line Items] |  |  |
Employee purchase price of common stock (as a percent) | 85.00% |  |
Customer One | Revenue Benchmark | Customer Concentration Risk |  |  |
Accounting Policies [Line Items] |  |  |
Concentration risk (as a percent) | 10.00% | 10.00% |
Minimum |  |  |
Accounting Policies [Line Items] |  |  |
Customer payment period | 30 days |  |
Settlement period (in days) | 1 day |  |
Useful life (in years) | 3 years |  |
Minimum | Computer software |  |  |
Accounting Policies [Line Items] |  |  |
Estimated useful life (in years) | 3 years |  |
Maximum |  |  |
Accounting Policies [Line Items] |  |  |
Customer payment period | 60 days |  |
Settlement period (in days) | 2 days |  |
Useful life (in years) | 7 years |  |
Maximum | Computer software |  |  |
Accounting Policies [Line Items] |  |  |
Estimated useful life (in years) | 5 years |  |

X
- Definition Accounting Policies [Line Items] + References No definition available. + Details
Name: | phr_AccountingPoliciesLineItems
Namespace Prefix: | phr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Contract With Customer, Payment Period + References No definition available. + Details
Name: | phr_ContractWithCustomerPaymentPeriod
Namespace Prefix: | phr_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of Third-Party Payment Processors + References No definition available. + Details
Name: | phr_NumberOfThirdPartyPaymentProcessors
Namespace Prefix: | phr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Settlement Assets, Settlement Period + References No definition available. + Details
Name: | phr_SettlementAssetsSettlementPeriod
Namespace Prefix: | phr_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 720 -SubTopic 35 -Section 50 -Paragraph 1 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=6420018&loc=d3e36677-107848 + Details
Name: | us-gaap_AdvertisingExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of allowance for credit loss on accounts receivable, classified as current. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5074-111524 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(4)) -URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 4 -URI https://asc.fasb.org/extlink&oid=126905981&loc=d3e2420-110228 + Details
Name: | us-gaap_AssetImpairmentCharges
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 42 -URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9054-108599 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 18 -URI https://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 20 -URI https://asc.fasb.org/extlink&oid=123594938&loc=d3e13531-108611 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=123594938&loc=d3e13537-108611 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 20 -URI https://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592 + Details
Name: | us-gaap_ConcentrationRiskPercentage1
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 18 -URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8672-108599 + Details
Name: | us-gaap_NumberOfOperatingSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Purchase price of common stock expressed as a percentage of its fair value. + References No definition available. + Details
Name: | us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_EmployeeStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=phr_CustomerOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_SalesRevenueNetMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_ComputerSoftwareIntangibleAssetMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |